Temperature sensing for monitoring or diagnosing performance of a device or a system is difficult or impractical in various industrial applications. For example, in-situ measurement of substrate temperature during processing of microelectronic circuits is usually difficult and time consuming, and in many cases impossible. Such processing steps include thermal anneal, plasma clean, baking, pre-heating, pre-cooling, etc.
Currently known methods for conducting such temperature measurements employ thermocouple wires. Typically, a pair of thermocouple wires is attached to a substrate. The substrate is then placed in the fabrication tool of interest. The thermocouple wires are routed to an instrument outside the tool through a feedthrough port or a gap between sealed surfaces. The instrument records the sensed temperature during tool operation. This approach has several disadvantages. First, it is intrusive to the usual environment within the tool, and may alter the environment sufficiently that the resultant measurements are unrepresentative of the actual conditions when the thermocouple wafer is not present. Second, the tool can not be used for the time required to obtain the data, which may extend for several hours. Third, interruption of the usual tool operation cycle and frequency may require additional time to restabilize the tool for production. Fourth, for some tools, the usual operating sequence may have to be bypassed in order to accomplish the measurement (for example, moving robots, etc. may have to be disabled). In some cases, the structure of the tool prohibits access to the process chamber during operation, so that the measurement cannot be made at all.
Therefore, there exists a need for a micro-electro-mechanical-system (MEMS) temperature sensor that enables in-situ or ex-situ temperature measurement of a system without employing thermocouple wires over a wide temperature range.